Why Grow in a Greenhouse?

Across most of North America, December is down time for market farmers. Days will keep getting shorter until the winter solstice on December 21st and, in most places, it's too cold for much of anything to grow. Greenhouse growers, though, are gearing up this month. It's time to start tomato, lettuce, and pepper seeds for transplanting into a heated greenhouse, followed shortly thereafter by transplant production for the unheated greenhouse. If working in the greenhouse sounds like therapy for the midwinter blues — not to mention a way to make some cash earlier next year — then read on to learn more about how greenhouse growing might fit into your business plan.

The Greenhouse Advantage

The obvious reason to grow greenhouse vegetables, flowers, and herbs is to have crops at a time of year when they can't be grown outdoors. Out-of-season tomatoes, cucumbers, lettuce, basil, and other vegetables command high prices in some markets. It's important to note, though, that the cost of winter production of warm-weather crops like tomatoes is very high, so don't jump into it unless you are certain you have a market and a price that will provide a return on your investment. Heating will be your biggest cost, followed by labor. And if you happen to have a long spell of overcast weather, you may also need to provide supplemental lighting.

Tools and Supplies for the Greenhouse

Greenhouse vegetables, herbs, and flowers can be grown in two systems: in-ground soil culture, or container culture. The first is easiest for beginners because watering and fertilization requirements are not as exacting. Growing in containers, though, has the advantages of no weeding and reduced incidence of soilborne diseases. So the determining factor may well be the type of greenhouse you own. If you have a transplant house with a concrete or gravel floor, you will have to grow in containers such as grow bags, bulb crates, or large pots. If you have a soil floor, you can choose which system to use.

What to Grow in Your Greenhouse

You can grow virtually anything in a greenhouse, but that protected space is prime real estate, so you should choose crops carefully to maximize profits and produce crops that don't do well outside for you. Tomatoes are the number-one greenhouse crop grown in the US, probably because demand is high and consistent year-round. Cucumbers are the second most popular greenhouse crop, followed by head lettuce and salad mix. Cut flowers can be profitable in a greenhouse. Among seed-grown flowers, the best choices are those that don't do well outside in the wind, such as delphinium, lisianthus, and snapdragons. In cool climates, heat-loving flowers such as celosia are good candidates for greenhouse growing. Among the herbs, basil can be grown earlier and later in the year in a greenhouse, and there is a consistent demand for it. Tender perennials herbs such as rosemary and thyme can be kept in the greenhouse as mother plants, then propagated in late winter to sell as container plants or culinary cut herbs in spring. Strawberries are another valuable greenhouse crop, and can be grown in hanging containers to keep floor space free for other crops.

As the days get shorter this month and you find yourself inside more frequently, spend some time reviewing the possibilities for greenhouse production. If you decide to go for it, now is the time to buy seeds and schedule sowing dates for a mid February to mid March planting. By April or May, you could have a greenhouse full of crops ready for market!